1. Field of the Invention
This invention relates in general to an independently steered wheeled framework which can assume the shape of a bicycle, tricycle, or other type vehicle, and is particularly adapted to and will be illustrated primarily in connection with a wheelchair.
2. Description of the Prior Art
From their early introduction, wheelchairs became very popular with disabled persons in or out of hospitals because they provided them with needed mobility.
A conventional wheelchair framework has vertically arranged, spaced apart tubular side frame members supporting a chair. Each side frame includes a horizontally disposed arm rest. Transverse axles are attached to the side frame members. Large rear wheels are journaled to the axles. Front-mounted small caster wheels support and direct the front end of the wheelchair. Each rear wheel has a hand-grip ring for hand propulsion and steering of the wheelchair.
Subsequently, various attachments to wheelchairs were proposed, using hand or foot propelled front wheels, in order to extend their range and speed of travel and to prevent rider fatigue which may result from prolonged use of the steering hand-grip rings.
In practice, such wheeled attachments were intended to convert a wheelchair framework from a stationary position, with its caster wheels on the ground, to a mobilized tricycle by adding a front wheel and elevating its caster wheels above ground.
It has also been suggested to immobilize such a tricycle by elevating the added front wheel and using its propulsion means for muscular exercise and rehabilitation purposes.
Such proposed attachments to wheelchairs are described, for example, in U.S. Pat. Nos. 4,720,117, 4,572,501 and, 4,824,132.
In general, such proposed wheeled attachments have been found by users to be difficult to mount on and dismount from a wheelchair. These attachments frequently require tools and/or the assistance from a caregiver. They are difficult to steer in a straight line, or over irregular, uneven and obstructed ground. They share the inherent problems of bicycles and tricycles: such as rider's early fatigue, especially over steep terrain due to the need for simultaneous movement of the pedals, front wheel and handlebar. Also, the rider tends to lean inward especially while negotiating sharp turns and around obstructions.
This "leaning inward" problem and the various proposed solutions thereto are well described in U.S. Pat. No. 4,720,117, starting at Col.1, ln.65 and ending at Col.2, ln.68, and such description is herein incorporated by reference.
But, since the attachment described in U.S. Pat. No. 4,720,117 is based on simultaneous movement of its hand cranks 18 and front wheel 30, it does not provide for independent steering of its wheel 30.
Accordingly, it is a main object of this invention to overcome the above-mentioned and other apparent drawbacks of known wheeled attachments and to provide a novel independently-steered wheeled framework.
It is a further object of this invention to eliminate the need for front caster wheels in wheelchairs.
It is yet a further object to allow the conversion of a wheelchair from outdoor use to indoor use to be easily accomplished by its user without the need for tools or assistance from others.